It is generally necessary to heat the fuel for a jet aircraft engine from, for example, -45.degree. F. at the tank to +40.degree. F. upstream of the fuel filter to preclude icing of the fuel filter. Present fuel heating systems often use heat rejected from the engine lube oil to accomplish this temperature rise. Yet another expedient is to extract heat from the engine exhaust. However, such systems have proved to be inadequate since they work well only at full power. Substantially less heat is available for heating the fuel at idle in cold day conditions.